Conductive Coupling Assembly

ABSTRACT

A method and apparatus for conducting an electrical current between a first transport member and a second transport member. In one illustrative embodiment, a coupling assembly comprises a first fitting associated with a first end of a first transport member, a second fitting associated with a second end of a second transport member, and a seal. The seal is configured for placement around the first fitting and the second fitting when the first end of the first transport member is positioned relative to the second end of the second transport member. The seal is further configured to seal an interface between the first transport member and the second transport member. The seal is comprised of a material configured such that the seal has a level of conductivity within a selected range and such that a conductive pathway is formed between the first transport member and the second transport member.

RELATED PROVISIONAL APPLICATIONS

This application is related to, and claims the benefit of priority of,the following provisional patent applications: Provisional Applicationfor Patent Ser. No. 61/657,248, filing date Jun. 8, 2012, entitled“Conductive Coupling Assembly;” Provisional Application for Patent Ser.No. 61/669,299, filing date Jul. 9, 2012, entitled “Composite Tubes fora Fluid Transport System;” and Provisional Application for Patent Ser.No. 61/712,930, filing date Oct. 12, 2012, entitled “Fluid TransportSystem for Preventing Electrical Discharge;” all of which areincorporated herein by reference.

CROSS-REFERENCES TO RELATED CASES

This application is related to the following patent applications:entitled “Composite Tubes for a Fluid Transport System,” filing date______, Ser. No. ______, attorney docket no. 12-0368-US-NP; and entitled“Fluid Transport System for Preventing Electrical Discharge,” Ser. No.______, filing date ______, attorney docket no. 12-0739-US-NP; filed ofeven date herewith, each assigned to the same assignee, and eachincorporated herein by reference.

BACKGROUND INFORMATION

1. Field:

The present disclosure relates generally to a fluid transport systemand, in particular, to a fluid transport system configured to have adesired electrical configuration. Still more particularly, the presentdisclosure relates to a method and apparatus for limiting the flow ofelectric current, induced by an event such as lightning or an electricalfault, along a fluid transport system and allowing static dissipationalong the fluid transport system.

2. Background:

A fluid transport system typically includes tubes connected together formoving fluid through the tubes. As used herein, a “fluid” may compriseany number of liquids and/or gases. Fluid transport systems may be usedto transport any number of fluids within vehicles, such as, for example,aircraft. A fluid transport system may include groups of tubes connectedin series, in parallel, or a combination of the two. In some cases,these tubes may be coupled together using, for example, withoutlimitation, coupling assemblies.

A fuel system is an example of one type of fluid transport system in anaircraft. Some currently available fuel systems comprise fuel tankscomprised of metal and/or composite materials, such as carbon fiberreinforced plastic (CFRP). When used in fuel tanks, fuel tubes comprisedof plastic and/or metal materials may be prone to the buildup ofelectrostatic charge. The buildup of electrostatic charge on a fuel tubemay be caused by a number of different factors including, but notlimited to, the flow of fuel through and/or around the fuel tube.

When electrostatic charge builds up on a surface of a fuel tube, thefuel tube may be prone to electrical discharge of this electrostaticcharge. This electrical discharge may be referred to as “staticdischarge.” Static discharge may take the form of, for example, anelectrical arc from the fuel tube to a nearby structure.

Further, when used in a fuel tank comprised of electrically resistivematerials such as, for example, carbon reinforced plastic, fuel tubescomprised of plastic and/or metal materials may also be prone tovoltages and currents induced by an electromagnetic event, such aslightning. In some situations, the induced voltages may lead toelectrical discharge in the form of electrical sparking and/or arcingfrom the tubes to one or more nearby structures. Additionally, in somesituations, the induced currents may lead to electrical discharge withinthe connections between tubes.

The voltage and currents induced by lightning may typically be small andwithin selected tolerances inside the fuel tanks of aircraft havingwings comprised of metal materials, such as, for example, aluminum.However, the voltages and currents induced by lightning inside the fueltanks of aircraft having wings comprised of non-metallic materials, suchas, for example, carbon fiber reinforced plastic, may be greater andoutside of selected tolerances. In particular, the higher electricalresistance of carbon fiber reinforced plastic as compared to aluminummay cause larger voltages and currents to be induced with respect to thetubes inside the fuel tanks.

Typically, with currently available aircraft, fuel transport systems usemetal tubing to transport fuel within fuel tanks. In an aircraftcomprised of carbon fiber reinforced plastic, the metal tubing may beprone to induced voltages that may cause undesired electricaldischarges. Some currently available methods for reducing the level orintensity of an undesired electrical discharge may include insertinghigh resistance electrical isolators into the metal tubing. Theseisolators may be used to constrain the currents and voltages that may beinduced by lightning, thereby reducing the level of any undesiredelectrical discharge that may occur.

However, the weight and expense needed to install metal systems havingthese isolators may be greater than desired. Part of the cost andexpense to install such metal systems with isolators may be the need toprotect the metal systems against arcing from the induced voltagesremaining in the system after the installation of the isolators.

Additionally, an electrical discharge within a fuel system caused by thebuildup of electrostatic charge and/or induced voltages and currents inresponse to an electromagnetic event such as lightning may presentsafety concerns. Therefore, it would be desirable to have a method andapparatus that takes into account at least some of the issues discussedabove, as well as other possible issues.

SUMMARY

In one illustrative embodiment, a coupling assembly comprises a firstfitting associated with a first end of a first transport member, asecond fitting associated with a second end of a second transportmember, and a seal. The seal is configured for placement around thefirst fitting and the second fitting when the first end of the firsttransport member is positioned relative to the second end of the secondtransport member. The seal is further configured to seal an interfacebetween the first end of the first transport member and the second endof the second transport member. The seal is comprised of a materialconfigured such that the seal has a level of conductivity within aselected range and such that a conductive pathway is formed between thefirst transport member and the second transport member.

In another illustrative embodiment, a fuel system comprises a firsttransport member, a second transport member, and a coupling assembly.The coupling assembly is configured to couple a first end of the firsttransport member to a second end of the second transport member. Thecoupling assembly comprises a first fitting associated with the firstend of the first transport member and having a level of conductivitywithin a selected range, a second fitting associated with the second endof the second transport member and having the level of conductivitywithin the selected range, a first gasket, a second gasket, and asleeve. The first gasket is configured for placement around the firstfitting. The first gasket comprises a viscoelastic material having thelevel of conductivity within the selected range. The second gasket isconfigured for placement around the second fitting. The second gasketcomprises the viscoelastic material having the level of conductivitywithin the selected range. The sleeve is configured for placement aroundthe first gasket and the second gasket and having the level ofconductivity within the selected range. The sleeve is configured tocompress the first gasket and the second gasket to form a seal thatseals an interface between the first end of the first transport memberand the second end of the second transport member when the first end ofthe first transport member is positioned relative to the second end ofthe second transport member. The seal forms a conductive pathway betweenthe first transport member and the second transport member through thefirst fitting, the seal, and the second fitting.

In yet another illustrative embodiment, a method for conducting anelectrical current between a first transport member and a secondtransport member in a fuel system in an aerospace vehicle is provided.The aerospace vehicle is operated such that an electrical charge buildsup around a surface of at least one of the first transport member andthe second transport member in the fuel system in the aerospace vehicle.A first end of the first transport member is coupled to a second end ofthe second transport member using a first fitting associated with thefirst end of the first transport member, a second fitting associatedwith the second end of the second transport member, and a seal. The sealis configured to seal an interface between the first end of the firsttransport member and the second end of the second transport member whenthe first end of the first transport member is positioned relative tothe second end of the second transport member. The seal is comprised ofa material configured such that the seal has a level of conductivitywithin a selected range and such that a conductive pathway is formedbetween the first transport member and the second transport member.Electrostatic charge that builds up on at least one of the firsttransport member and the second transport member during operation of theaerospace vehicle is dissipated using the conductive pathway formed bythe seal between the first transport member and the second transportmember.

The features and functions can be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives, and features thereof will best be understood by reference tothe following detailed description of an illustrative embodiment of thepresent disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a fluid transport system in the form of ablock diagram in accordance with an illustrative embodiment;

FIG. 2 is an illustration of a transport member in the form of a blockdiagram in accordance with an illustrative embodiment;

FIG. 3 is an illustration of a connection in the form of a block diagramin accordance with an illustrative embodiment;

FIG. 4 is an illustration of tubes configured for use in a fluidtransport system in accordance with an illustrative embodiment;

FIG. 5 is an illustration of components for a coupling assembly inaccordance with an illustrative embodiment;

FIG. 6 is an illustration of a partially-assembled coupling assembly inaccordance with an illustrative embodiment;

FIG. 7 is an illustration of a fully-assembled coupling assembly inaccordance with an illustrative embodiment;

FIG. 8 is an illustration of a cross-sectional view of a couplingassembly in accordance with an illustrative embodiment;

FIG. 9 is an illustration of a cross-sectional view of a differentconfiguration for a coupling assembly in accordance with an illustrativeembodiment;

FIG. 10 is an illustration of a cross-sectional view of anotherconfiguration for a coupling assembly in accordance with an illustrativeembodiment;

FIG. 11 is an illustration of a cross-sectional view of a differentconfiguration for a coupling assembly in accordance with an illustrativeembodiment;

FIG. 12 is an illustration of a process for reducing an intensity of anelectrical discharge within a fluid transport system in the form of aflowchart in accordance with an illustrative embodiment;

FIG. 13 is an illustration of a process for reducing the energy that canbe supplied to an electrical discharge within a fluid transport systemin the form of a flowchart in accordance with an illustrativeembodiment;

FIG. 14 is an illustration of a process for dissipating electrostaticcharge in the form of a flowchart in accordance with an illustrativeembodiment;

FIG. 15 is an illustration of an aircraft manufacturing and servicemethod in the form of a flowchart in accordance with an illustrativeembodiment; and

FIG. 16 is an illustration of an aircraft in the form of a block diagramin accordance with an illustrative embodiment.

DETAILED DESCRIPTION

The different illustrative embodiments recognize and take into accountdifferent considerations. For example, the different illustrativeembodiments recognize and take into account that it may be desirable tohave a fluid transport system configured to reduce the intensity ofelectrical discharge from components, such as, for example, tubes,within the fluid transport system.

The different illustrative embodiments recognize and take into accountthat tubes comprised of materials with high electrical resistance levelsmay be used in a fluid transport system to reduce the intensity ofelectrical discharge caused by voltages and currents induced in responseto an electromagnetic event such as, for example, lightning. High levelsof electrical resistance may include levels above, for example, about100 kilohms per meter length of tube.

Materials with high levels of electrical resistance include, but are notlimited to, nonmetallic fiber reinforced composite materials, carbonreinforced plastic materials, plastic materials, non-homogenous metallicmaterials, and/or other types of materials. The illustrative embodimentsrecognize and take into account that tubes comprised of any of thesetypes of materials may limit the levels of voltages and currents inducedin response to the occurrence of an electromagnetic event, therebyreducing the intensity of any electrical discharge caused by theseinduced voltages and/or currents.

For example, materials having high levels electrical resistance maylimit the current induced along a tube in response to an electromagneticevent, such as lightning. With fuel tubes in a fuel system, limiting theflow of current along these fuel tubes may limit the voltages inducedacross the connections between these fuel tubes when the electricalresistance of these connections is lower than the electrical resistancethrough a specified length of fuel tube connected to the connection. Thespecified length, for example, may be 0.3 meters of tube. In thismanner, electrical discharge in the form of electrical sparking and/orarcing may be reduced and/or prevented. Consequently, the illustrativeembodiments recognize and take into account that an upper limit forresistivity or, equivalently, a lower limit for conductivity, may beselected for the materials used in the connections between fuel tubes toreduce electrical discharge across these connections and along the fueltubes.

However, the illustrative embodiments recognize and take into accountthat in some cases, if a conductive material were to become dislodgedfrom a connection between fuel tubes and form a bridge between a metalfuel tube and a structure within the fuel tank, the conductive materialcould short circuit this bridge and allow, for example, lightning toinduce a flow of current or possibly a spark from the fuel tube to thestructure. As a result, the illustrative embodiments recognize and takeinto account that the resistivity of the conductive material may requirea lower limit for resistivity, or equivalently, an upper limit forconductivity.

However, the different illustrative embodiments recognize and take intoaccount that in other cases, fuel tubes may be used in metallic fueltanks in which lightning induced voltages and/or currents may be withinselected tolerances. Consequently, the materials used in the connectionsbetween fuel tubes may only need to be selected to allow dissipation ofelectrostatic charge that has built up along these fuel tubes.Consequently, the illustrative embodiments recognize and take intoaccount that only an upper limit for resistivity or, equivalently, alower limit for conductivity, may need to be selected for the materialsused in the connections between fuel tubes to reduce electricaldischarge across these connections.

Further, the illustrative examples recognize and take into account thatthe possibility of a static discharge caused by the build-up ofelectrostatic charge may be reduced and/or prevented by grounding fueltubes to a structure having a resistance that is sufficiently low toremove electrostatic charge from the fuel tubes at a rate faster thanthe electrostatic charge can build up on the fuel tubes such that a netcharge on the fuel tubes within selected tolerances may be maintained.In particular, a net charge on the fuel tubes may be reduced to withinselected tolerances. The different illustrative embodiments recognizeand take into account that when fuel tubes are connected in series,electrostatic charge may be removed from the series of fuel tubes byusing conductive pathways through the connections between the fuel tubesand then grounding the series to the structure.

Thus, the different illustrative embodiments provide a system and methodfor reducing an intensity of electrical discharge within a fluidtransport system. In one illustrative embodiment, the fluid transportsystem is located within a vehicle, such as an aerospace vehicle.Further, the fluid transport system may be comprised of materialsselected such that the fluid transport system has a selected electricalconfiguration. This electrical configuration for the fluid transportsystem may be selected such that electrical discharge that occurs withinthe fluid transport system during operation of the aerospace vehicle maybe reduced to within selected tolerances.

Referring now to the figures and, in particular, with reference to FIG.1, an illustration of a fluid transport system in the form of a blockdiagram is depicted in accordance with an illustrative embodiment. Fluidtransport system 100 is configured to transport materials withinplatform 104.

The materials transported may include any number of liquid materials,gaseous materials, and/or solid materials. As one illustrative example,fluid transport system 100 may be used to transport fluid 102 withinplatform 104. Fluid 102 may comprise any number of liquids and/or gases.

In one illustrative example, platform 104 takes the form of aerospacevehicle 106. In this illustrative example, fluid transport system 100may take the form of fuel system 105 configured to transport fluid 102in the form of fuel 108 within aerospace vehicle 106. Aerospace vehicle106 may be selected from one of an aircraft, a helicopter, an unmannedaerial vehicle (UAV), a space shuttle, or some other suitable type ofvehicle configured to travel in air and/or space. Of course, in otherillustrative examples, platform 104 may take the form of a groundvehicle, a water vehicle, or some other suitable type of vehicle.

As depicted, fluid transport system 100 comprises plurality of transportmembers 110 and number of connections 112. As used herein, a “pluralityof” items means two or more items. Further, a “number of” items meansone or more items. For example, plurality of transport members 110 meanstwo or more transport memebers, while number of connections 112 meansone or more connections.

As used herein, a “transport member,” such as one of plurality oftransport members 110, may be any structural member having a channelthrough which materials may be moved. Depending on the implementation, atransport member in plurality of transport members 110 may take the formof, for example, a tube, a duct, a cylinder, a pipe, a pipeline, aconduit, or some other type of structure having a channel through whichmaterials may flow. As one illustrative example, plurality of transportmembers 110 may take the form of plurality of tubes 111.

Further, as used herein, a “connection,” such as one of number ofconnections 112, may be any type of permanent or removable physicalconnection between two or more transport members in plurality oftransport members 110. Depending on the implementation, a connection innumber of connections 112 may comprise any number of components such as,for example, without limitation, fasteners, joint elements, screws,ferrules, rings, seals, adhesive bonds, and/or other types ofcomponents.

As one illustrative example, number of connections 112 may take the formof number of coupling assemblies 113. Each coupling assembly in numberof coupling assemblies 113 may be configured to couple a transportmember in plurality of transport members 110 with another transportmember in plurality of transport members 110. In this manner, whenplurality of transport members 110 takes the form of plurality of tubes111, number of coupling assemblies 113 may be used to couple tubes inplurality of tubes 111 to each other.

As used herein, a first component, such as a tube, “coupled” to a secondcomponent, such as another tube, means that the first component isconnected to or fastened to the second component. This connection may bea direct connection or an indirect connection. For example, an end ofone tube may be coupled to the end of another tube using a couplingassembly. With a direct connection, the end of the tube may come intocontact with the end of the other tube when these two ends are coupled.With an indirect connection, the end of the tube and the end of theother tube may not contact each other when these two ends are coupled.

Of course, in other illustrative examples, number of connections 112 maytake other forms. For example, transport members may be attached to eachother using other methods, such as, for example, applying adhesives topermanently connect transport members or performing thermoplasticwelding operations.

In these illustrative examples, fluid transport system 100 is configuredsuch that fluid transport system 100 has selected electricalconfiguration 114. Selected electrical configuration 114 may becomprised of set of electrical properties 116, each having a valuewithin a selected range. As used herein, a “set of” items means one ormore items.

Set of electrical properties 116 may include, for example, resistance,resistivity, conductivity, and/or other types of electrical properties.Further, in some cases, any component that makes up fluid transportsystem 100 may be configured such that the component also has a set ofelectrical properties with values within selected ranges.

Selected electrical configuration 114 may be selected such that anintensity of electrical discharge that occurs within fluid transportsystem 100 during operation of aerospace vehicle 106 may be reduced towithin selected tolerances. In particular, selected electricalconfiguration 114 may be selected such that voltages and currents,induced within fluid transport system 100 in response to anelectromagnetic event such as lighting, may be constrained to withinselected tolerances. Still further, selected electrical configuration114 may be selected to allow dissipation of electrostatic charge thatmay build up along plurality of transport members 110 during operationof aerospace vehicle 106.

Turning now to FIG. 2, an illustration of a transport member inplurality of transport members 110 from FIG. 1 in the form of a blockdiagram is depicted in accordance with an illustrative embodiment.Transport member 200 in FIG. 2 is an example of one implementation for atransport member in plurality of transport members 110 in FIG. 1. In oneillustrative example, transport member 200 takes the form of tube 201.Tube 201 may be an example of one implementation for a tube in pluralityof tubes 111 in FIG. 1.

As depicted, transport member 200 has first end 202 and second end 204.Further, transport member 200 has outer surface 203 and inner surface205. Inner surface 205 may form channel 206 that extends along axis 215through transport member 200 from first end 202 of transport member 200to second end 204 of transport member 200. Axis 215 may be a center axisthat extends through transport member 200 from first end 202 oftransport member 200 to second end 204 of transport member 200. Fluid102 from FIG. 1 may be carried within channel 206.

In these illustrative examples, connection 218 may be an example of aconnection in number of connections 112 that may be used to connecttransport member 200 to another transport member in plurality oftransport members 110 in FIG. 1. As depicted, connection 218 may be usedat either first end 202 of transport member 200 or second end 204 oftransport member 200 to connect transport member 200 to anothertransport member.

In one illustrative example, connection 218 takes the form of couplingassembly 220. Coupling assembly 220 may comprise any number ofcomponents such as, for example, without limitation, fasteners, jointelements, screws, ferrules, rings, seals, and/or other types ofcomponents.

In these illustrative examples, transport member 200 may be comprised ofmaterial 207. Material 207 may be selected such that transport member200 has electrical configuration 210. Electrical configuration 210 maycomprise set of electrical properties 212, each having a value within aselected range. In one illustrative example, set of electricalproperties 212 includes resistance 214. Resistance 214 may be electricalresistance in these examples.

As used herein, the “resistance” of an item, such as transport member200, is the opposition of the item to the flow of electric currentthrough the item. In this manner, resistance 214 of transport member 200may be the opposition of transport member 200 to the flow of electriccurrent through transport member 200.

Material 207 may be selected such that resistance 214 is within selectedrange 216. Selected range 216 for resistance 214 may be selected suchthat resistance 214 is sufficiently high to limit the voltages andcurrents, induced along transport member 200 in response to anelectromagnetic event, to within selected tolerances. Theelectromagnetic event may be, for example, a lightning strike, a shortcircuit, an overloaded circuit, an electrical field, or some other typeof electromagnetic event.

In particular, material 207 may be selected such that the inducedvoltages and currents may be limited to levels at or below the level atwhich an undesired electrical discharge may be formed. The undesiredelectrical discharge may be, for example, an arc between transportmember 200 and a structure and/or a spark in connection 218 having atleast one property outside of selected tolerances.

In one illustrative example, when transport member 200 is installedwithin a particular specified electromagnetic environment, selectedrange 216 for resistance 214 of transport member 200 may be selectedsuch that the per unit length resistance 214 of transport member 200 isat or above about 100 kilohms per meter (kΩ/m). For example, whentransport member 200 is installed in a fuel tank of an aircraftcomprised of carbon fiber reinforced plastic, the specifiedelectromagnetic environment may be a specified lightning environment.

Further, when transport member 200 is configured to allow staticdissipation and reduce and/or prevent the build-up of electrostaticcharge, selected range 216 for resistance 214 of transport member 200may be selected such that the per unit length resistance 214 oftransport member 200 is at or below about 100 megohms per meter (MΩ/m).

Material 207 may take a number of different forms. Material 207 maycomprise, for example, without limitation, non-metallic fiber reinforcedcomposite materials, plastic materials, and/or other suitable types ofnon-homogeneous metallic materials. In one illustrative example,material 207 takes the form of composite material 208 comprised of anynumber of non-metallic materials. When comprised of composite material208, transport member 200 may be referred to as a composite transportmember. In this manner, tube 201 may be referred to as a composite tube.

In this manner, selected range 216 may include levels of resistance 214sufficiently low to provide static dissipation. Further, selected range216 may include levels of resistance 214 sufficiently high to limit thevoltages and currents induced along transport member 200 in response toan electromagnetic event.

Further, in these illustrative examples, resistance 214 of transportmember 200 may vary along axis 215. However, composite material 208 maybe selected such that resistance 214 does not vary outside of selectedtolerances. For example, transport member 200 may be formed usingcomposite material 208 selected such that resistance 214 of transportmember 200 may vary only by less than a selected percentage over thelength of the transport member and time with respect to axis 215. Thisselected percentage may be between about 20 percent and about 40 percentin one illustrative example.

In one illustrative example, each transport member in plurality oftransport members 110 in FIG. 1 may be implemented in a manner similarto transport member 200. Resistance within selected range 216 may bedistributed evenly over individual intervals of length of tubinginstalled in fluid transport system 100 in FIG. 1.

When fluid transport system 100 takes the form of fuel system 105 inFIG. 1 located in a fuel tank, the distributed high electricalresistance may keep the electromagnetic fields inside the fuel tankinduced by lightning from being concentrated, thereby reducing thevoltages and currents induced along the tubing. The per unit lengthresistance with respect to particular lengths of tubing in fuel system105 may be different between different length intervals, but evenlydistributed within these length intervals.

With reference now to FIG. 3, an illustration of a connection in numberof connections 112 from FIG. 1 in the form of a block diagram isdepicted in accordance with an illustrative embodiment. Connection 300is an example of one implementation for a connection in number ofconnections 112 in FIG. 1. Connection 300 may take the form of couplingassembly 301. Coupling assembly 301 may be an example of oneimplementation for a coupling assembly in number of coupling assemblies113 in FIG. 1.

In some cases, connection 300 may be used to implement connection 218 inFIG. 2. For example, coupling assembly 301 may be used to implementcoupling assembly 220 in FIG. 2.

As depicted, connection 300 is used to couple first transport member 302with second transport member 304. In particular, first end 306 of firsttransport member 302 is coupled to second end 308 of second transportmember 304 using connection 300. First transport member 302 has firstsurface 310 and first channel 312. Second transport member 304 hassecond surface 314 and second channel 316.

First channel 312 and second channel 316 may be configured to allowdifferent types of materials to flow through first transport member 302and second transport member 304, respectively. These materials mayinclude any number of liquid materials, gaseous materials, and/or solidmaterials. In one illustrative example, first transport member 302 andsecond transport member 304 may be a first fuel transport member and asecond fuel transport member, respectively, through which fuel 108 fromFIG. 1 is allowed to flow.

When first end 306 of first transport member 302 is coupled to secondend 308 of second transport member 304, material may flow between firstchannel 312 within first transport member 302 and second channel 316within second transport member 304. In this manner, first channel 312and second channel 316 may form a channel that extends through bothfirst transport member 302 and second transport member 304 when firsttransport member 302 and second transport member 304 are coupled to eachother.

In these illustrative examples, connection 300 may be configured suchthat the electrical resistance across connection 300 is less than theelectrical resistance through a specified length of first transportmember 302 and through a specified length of second transport member304. This specified length may be, for example, without limitation,about one foot (ft) or about one third of a meter (m) when connection300 is implemented within a fuel tank in an aircraft comprised of carbonfiber reinforced plastic. In particular, this specified length may applywhen first transport member 302, second transport member 304, andconnection 300 are comprised of similarly non-metallic highlyelectrically resistive materials.

In this manner, each of the individual components that make upconnection 300 may be configured such that the electrical resistanceacross connection 300 is less than the electrical resistance through thespecified length of first transport member 302 and through the specifiedlength of second transport member 304. The components that make upconnection 300 may be comprised of any number of materials including,but not limited to, metal, plastic, a composite material, and/or othertypes of materials.

If components having an electrical resistance outside of the selectedrange are used in forming connection 300, the size and/or placement ofthese pieces relative to first transport member 302 and second transportmember 304 may have restrictions. As one illustrative example, if apiece of metal having an electrical resistance outside of the selectedrange is used, the piece may need to have electrical ground paths to andthrough first transport member 302, second transport member 304, and/orother transport members. This type of grounding may allow staticdissipation from tube to tube through the piece of metal and from thepiece of metal to ground through one of the tubes.

In one illustrative example, connection 300 may include first fitting318, second fitting 320, seal 322, and cover 324. First fitting 318 andsecond fitting 320 are associated with first end 306 of first transportmember 302 and second end 308 of second transport member 304,respectively. In particular, first fitting 318 is associated with firstsurface 310 of first transport member 302 at first end 306 of firsttransport member 302. Further, second fitting 320 is associated withsecond surface 314 of second transport member 304 at second end 308 ofsecond transport member 304.

When one component is “associated” with another component, as usedherein, this association is a physical association. For example, a firstcomponent, such as first fitting 318, may be considered to be associatedwith a second component, such as first transport member 302, by beingsecured to the second component, bonded to the second component, mountedto the second component, welded to the second component, fastened to thesecond component, and/or connected to the second component in some othersuitable manner. The first component also may be connected to the secondcomponent using a third component. Additionally, the first component mayalso be considered to be associated with the second component by beingformed as part of and/or an extension of the second component.

In one illustrative example, first fitting 318 takes the form of firstferrule 326, and second fitting 320 takes the form of second ferrule328. As used herein, a “ferrule,” such as first ferrule 326 and secondferrule 328, is a ring-type object used for fastening, joining, and/orreinforcement. A ferrule may take the form of a ring, a bracelet, asleeve, a circular clamp, a spike, a band, or some other suitable typeof object.

First ferrule 326 is placed around first surface 310 of first transportmember 302 at first end 306 of first transport member 302. Secondferrule 328 is placed around second surface 314 of second transportmember 304 at second end 308 of second transport member 304.

In these illustrative examples, seal 322 is configured for placementaround first fitting 318 and second fitting 320 when first end 306 offirst transport member 302 is positioned relative to second end 308 ofsecond transport member 304. For example, seal 322 may be placed aroundfirst end 306 and second end 308 when first end 306 is positionedagainst second end 308.

Seal 322 is configured to seal interface 330 formed between first end306 of first transport member 302 and second end 308 of second transportmember 304 when first end 306 of first transport member 302 and secondend 308 of second transport member 304 are positioned relative to eachother. Sealing interface 330 means reducing the possibility of materialflowing into and/or out of the channel formed by first channel 312within first transport member 302 and second channel 316 within secondtransport member 304 at interface 330 when first transport member 302 iscoupled to second transport member 304.

In some illustrative examples, seal 322 may be configured such thatconnection 300 has electrical configuration 329. Electricalconfiguration 329 comprises set of electrical properties 333, eachhaving a value within a selected range. Electrical configuration 329 forconnection 300 may be selected such that connection 300 forms conductivepathway 331 between first transport member 302 and second transportmember 304.

Conductive pathway 331 may be a pathway that allows an electricalcurrent to flow between first transport member 302 and second transportmember 304. In other words, conductive pathway 331 allows an electricalcurrent to be conducted between first transport member 302 and secondtransport member 304. For example, electrical currents flowing throughfirst surface 310 of first transport member 302 may be conducted tosecond surface 314 of second transport member 304 when conductivepathway 331 is present. In this manner, electrostatic charge may bedissipated using conductive pathway 331 formed by connection 300.

In an illustrative example, at least a portion of seal 322 comprisesviscoelastic material 332. Viscoelastic material 332 is a material thatcomprises both viscous and elastic properties. A viscous material is amaterial that is resistant to being deformed by shear forces. An elasticmaterial is a material that can return to its original shape after thestress that caused deformation of the material is no longer applied.

In these illustrative examples, viscoelastic material 332 isnonmetallic. Further, viscoelastic material 332 may be selected suchthat viscoelastic material 332 has a level of conductivity 335 withinselected range 334 in these examples.

Selected range 334 may be selected such that conductive pathway 331 isformed between first transport member 302 and second transport member304 when first transport member 302 is coupled to second transportmember 304 using connection 300. In this illustrative example, selectedrange 334 may include levels of conductivity sufficiently high to allowelectrostatic charge that builds up on first transport member 302 and/orsecond transport member 304 to be dissipated through seal 322.

However, in some cases, selected range 334 may also include levels ofconductivity sufficiently low to reduce voltages and currents, inducedin response to an electromagnetic event, such as, for example,lightning, along first transport member 302 and/or second transportmember 304.

For example, selected range 334 may be between about 1×10⁻⁴Siemens/centimeters (S/cm) and about 1×10⁻⁹ Siemens/centimeters (S/cm).Of course, in other illustrative examples, selected range 334 may be aparticular level of conductivity between about 1×10⁻⁴Siemens/centimeters and about 1×10⁻⁹ Siemens/centimeters. Of course, inother illustrative examples, the upper limit and/or lower limit forselected range 334 may be different, depending on the particularimplementation for seal 322.

Selected range 334 of conductivity 335 may also be the range selectedfor the conductivity of other components within connection 300, firsttransport member 302, and/or second transport member 304. Further, firsttransport member 302, second transport member 304, first fitting 318,second fitting 320, seal 322, and cover 324 may together have a level ofconductivity that is within selected range 334.

Conductivity is related to resistivity. The resistivity of an item isthe ability of that item to prevent an electrical current from beingconducted through the item. In particular, conductivity is thereciprocal of resistivity. As the conductivity of an item increases, theresistivity of the item decreases. Similarly, as the conductivity of anitem decreases, the resistivity of the item increases. Selected range334 for conductivity 335 corresponds to a range for resistivity betweenabout 1×10⁴ ohms-centimeters (Ω-cm) and about 1×10⁹ ohms-centimeters(Ω-cm).

Viscoelastic material 332 may be selected from any number of materialsconfigured to provide a level of conductivity 335 within selected range334. For example, viscoelastic material 332 may comprise at least one ofa conductive elastomer, a conductive rubber, a conductive siliconematerial, and other suitable types of materials. An elastomer is apolymer that is viscoelastic.

As used herein, the phrase “at least one of,” when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of each item in the list may be needed. Forexample, “at least one of item A, item B, and item C” may include,without limitation, item A or item A and item B. This example also mayinclude item A, item B, and item C, or item B and item C. In otherexamples, “at least one of” may be, for example, without limitation, twoof item A, one of item B, and 30 of item C; four of item B and seven ofitem C; or some other suitable combination.

In these illustrative examples, seal 322 comprises first gasket 336,second gasket 338, and sleeve 340. As used herein, a “gasket,” such asfirst gasket 336 and second gasket 338, is a mechanical seal. In oneillustrative example, first gasket 336 takes the form of first O-ring342, and second gasket 338 takes the form of second O-ring 344. As usedherein, an “O-ring,” such as first O-ring 342 and second O-ring 344, isa mechanical gasket in the shape of a torus. Further, an O-ring has aloop-type shape.

Of course, in other illustrative examples, first gasket 336 and secondgasket 338 may take some other suitable form. For example, in somecases, first gasket 336 and second gasket 338 may be configured suchthat a cross-section of these gaskets has a triangular shape, a squareshape, a rectangular shape, an oval shape, or some other suitable typeof shape.

First O-ring 342 and second O-ring 344 are configured to be received byfirst fitting 318 and second fitting 320, respectively. As oneillustrative example, first O-ring 342 may fit into a groove aroundfirst fitting 318, and second O-ring 344 may fit into a groove aroundsecond fitting 320.

Sleeve 340 is then placed around first O-ring 342 and second O-ring 344to apply pressure to first O-ring 342 and second O-ring 344. Thispressure compresses first O-ring 342 and second O-ring 344 and causesthese O-rings to seal interface 330 between first end 306 of firsttransport member 302 and second end 308 of second transport member 304.

Additionally, in some illustrative examples, cover 324 may be placedover seal 322, at least a portion of first fitting 318, and at least aportion of second fitting 320. Cover 324 may be used to cover seal 322and hold seal 322 in place. In one illustrative example, cover 324 takesthe form of clamshell device 346.

When interface 330 has been sealed using seal 322, conductive pathway331 is formed between first transport member 302 and second transportmember 304. As one illustrative example, first O-ring 342 and secondO-ring 344 may be comprised of viscoelastic material 332 having a levelof conductivity within selected range 334. Further, each of firstfitting 318, second fitting 320, and sleeve 340 may be comprised of anonmetallic material having a level of conductivity within selectedrange 334.

In this illustrative example, conductive pathway 331 may be formedthrough first transport member 302, through first fitting 318, throughfirst O-ring 342, through sleeve 340, through second O-ring 344, throughsecond fitting 320, and through second transport member 304. Whenconductive pathway 331 is formed, an electrical current may flow in oneof a first direction and a second direction.

The first direction may be from first transport member 302, throughfirst fitting 318, through first O-ring 342, through sleeve 340, throughsecond O-ring 344, through second fitting 320, and to second transportmember 304. The second direction may be from second transport member304, through second fitting 320, through second O-ring 344, throughsleeve 340, through first O-ring 342, through first fitting 318, and tofirst transport member 302.

In this manner, electrical currents induced by electrostatic charge thatbuilds up on first surface 310 of first transport member 302 and/orsecond surface 314 of second transport member 304 may be dissipatedusing conductive pathway 331. In particular, with connection 300coupling first transport member 302 and second transport member 304,first transport member 302 and second transport member 304 may beconsidered grounded to each other.

In other words, an electrical current flowing into first transportmember 302 may flow into second transport member 304 through couplingassembly 301 without interruption and without the level of theelectrical current changing outside of selected tolerances. Similarly,an electrical current flowing into second transport member 304 may flowinto first transport member 302 through coupling assembly 301 withoutinterruption and without the level of the electrical current changingoutside of selected tolerances.

In some cases, the electrical current traveling along conductive pathway331 may be electrical current induced in response to an electromagneticevent such as, for example, a lightning strike. Selected range 334 ofconductivity 335 may be selected such that the voltage drop across firstO-ring 342 and the voltage drop across second O-ring 344 when this typeof electrical current travels through first O-ring 342 and second O-ring344, respectively, is reduced to within selected tolerances.

In these illustrative examples, first transport member 302 and secondtransport member 304 may be fuel tubes in, for example, fuel system 105in aerospace vehicle 106 in FIG. 1. In some cases, fuel system 105 maybe configured such that fuel system 105 has an overall level ofconductivity within selected range 334. Different portions of fuelsystem 105 may have different levels of conductivity and differentranges which apply to different portions of the fuel system. Someportions of the system may not be required to be within the range ofconductivity specified. The one or more levels of conductivity withinselected range 334 may be lower than the levels of conductivity forother portions of aerospace vehicle 106. For example, fuel system 105may have a level of conductivity between about 1×10⁻⁴Siemens/centimeters and about 1×10⁻⁹ Siemens/centimeters. However, oneor more other portions of aerospace vehicle 106 may have a level ofconductivity above about 1×10⁻⁴ Siemens/centimeters.

In this manner, fluid transport system 100 in FIG. 1 having plurality oftransport members 110, each implemented in a manner similar to transportmember 200 in FIG. 2, and number of connections 112, each implemented ina manner similar to connection 300 in FIG. 3, may be configured toreduce electrical discharge within fluid transport system 100. Pluralityof transport members 110, interconnected within fluid transport system100 may have high electrical resistance levels substantially evenlydistributed throughout this interconnected system of tubing.

In particular, the voltages and currents induced by lightning may bereduced and/or limited such that the energy imparted to the electricaldischarge may be reduced. In this manner, the undesired effects ofelectrical discharge within fluid transport system 100 may be reducedand/or prevented. In particular, the overall energy supplied to theelectrical discharge may be constrained to within selected tolerances.

In some cases, when implementing fluid transport system 100 comprisingan interconnected network of high electrical resistance transportmembers, such as plurality of transport members 110, the network oftransport members may need to be grounded to structure at one or morepoints for the purposes of removing electrostatic charge build-up andconstraining the lightning-induced voltages to the transport members.The transport members also may need to be grounded at the penetrationsof an enclosure encompassing an electrically shielded volume in whichfluid transport system 100 is installed, such as a fuel tank, in orderto reduce the possibility of a portion of an external electromagneticenvironment such as lightning or an electrical fault, entering thevolume.

Grounds made to structure for the purpose of removing electrical chargeto prevent electrostatic charge from building up along the transportmembers may be located at one or more places in fluid transport system100 as a means to ensure that an electrical path exists though fluidtransport system 100 from any point in fluid transport system 100 tostructure or ground with a sufficiently low resistance to dissipate theelectrostatic charge at a fast enough rate to prevent static chargebuild up at the point. In an electrostatic charging environment such asa fuel tank on an aircraft, an acceptable electrical resistance forproviding the capability to dissipate electrostatic charge from a pointon a tube though a path to structure or ground may be a value at orbelow about 100 megohms (MΩ).

In such case, grounds made for this purpose need only assure that thisoverall ground path resistance is accomplished. As such, a static groundresistance may be a value up to about 100 megohms (MΩ) in the limitingcase, but in the usual case a value up to about 10 MΩ.

Grounds made to structure for the purpose of constraining the lightninginduced voltages in the network of transport members in fluid transportsystem 100 may be located at one or more places in fluid transportsystem 100 as a means to ensure that the induced voltage from transportmember to transport member and from transport member to structure at anypoint in fluid transport system 100 is less than a selected threshold.Grounds made to structure on the perimeter of a fuel tank for thepurpose of shielding the fuel tank may be located at one or more placesin the perimeter to prevent undesired voltages and currents frompenetrating the fuel tank by means of conductive members to which saidvoltages and currents are induced by an external environment such aslightning outside the tank.

The illustrations of fluid transport system 100 in FIG. 1, transportmember 200 in FIG. 2, and connection 300 in FIG. 3 are not meant toimply physical or architectural limitations to the manner in which anillustrative embodiment may be implemented. Other components in additionto or in place of the ones illustrated may be used. Some components maybe optional. Also, the blocks are presented to illustrate somefunctional components. One or more of these blocks may be combined,divided, or combined and divided into different blocks when implementedin an illustrative embodiment.

In some illustrative examples, transport member 200 may have additionalfeatures not depicted in FIG. 2. For example, without limitation, one ormore structural features may extend into channel 206 from inner surface205 of transport member 200. These structural features may need to betaken into account when measuring resistance 214 for transport member200.

In other illustrative examples, seal 322 may comprise only gasket 352.Gasket 352 is configured to be placed around first fitting 318 andsecond fitting 320. Gasket 352 may have a shape configured for placementaround first fitting 318 and second fitting 320. For example, gasket 352may have a first end that fits into a groove around first fitting 318and a second end that fits into a groove around second fitting 320 whenfirst end 306 of first transport member 302 is positioned relative tosecond end 308 of second transport member 304. Further, gasket 352 maycomprise viscoelastic material 332 having a level of conductivity withinselected range 334.

With this type of configuration for seal 322 in connection 300, cover324 is used to compress gasket 352 to seal interface 330 between firstend 306 of first transport member 302 and second end 308 of secondtransport member 304, instead of sleeve 340. Further, with thisconfiguration for seal 322, conductive pathway 331 is formed throughfirst transport member 302, through first fitting 318, through gasket352, through second fitting 320, and through second transport member304.

In still other illustrative examples, seal 322 may include one or moregaskets in addition to first gasket 336 and second gasket 338. Forexample, seal 322 may also include a third O-ring configured forplacement around first fitting 318 and a fourth O-ring configured forplacement around second fitting 320.

These additional O-rings may be positioned such that cover 324compresses the third O-ring and the fourth O-ring instead of sleeve 340.Further, the third O-ring and the fourth O-ring provide an additionalconductive pathway. This additional conductive pathway is through firsttransport member 302, through first fitting 318, through the thirdO-ring, through cover 324, through the fourth O-ring, through secondfitting 320, and through second transport member 304.

In some illustrative examples, first fitting 318 and/or second fitting320 may not be considered part of connection 300. For example, whenfirst fitting 318 and second fitting 320 are part of first transportmember 302 and second transport member 304, respectively, these fittingsmay be considered separate from connection 300. In other illustrativeexamples, cover 324 may not be considered part of connection 300. Forexample, in some cases, connection 300 may include only seal 322.

With reference now to FIG. 4, an illustration of tubes configured foruse in a fluid transport system is depicted in accordance with anillustrative embodiment. In FIG. 4, tube 402, tube 404, and tube 406 maybe configured for use in a fluid transport system, such as, for example,fluid transport system 100 in FIG. 1. In particular, tube 402, tube 404,and tube 406 are examples of implementations of tubes in plurality oftubes 111 in FIG. 1. Further, each of tube 402, tube 404, and tube 406may be implemented in a manner similar to tube 201 in FIG. 2.

In this illustrative example, tube 402, tube 404, and tube 406 arecomprised of non-metallic composite materials and configured to have aresistance within a selected range. This selected range may be betweenabout 100 kilohms per meter to about 100 megohms per meter along axis405 through tube 402, tube 404, and tube 406. With each of tube 402,tube 404, and tube 406 having a resistance within the selected rangewith respect to axis 405, the flow of an electric current, induced inresponse to an electromagnetic event around these tubes, though thesetubes may be limited to within selected tolerances. Axis 405 is a centeraxis for tube 402, tube 404, and tube 406.

The illustration of tube 402, tube 404, and tube 406 in FIG. 4 are notmeant to imply physical or architectural limitations to the manner inwhich an illustrative embodiment may be implemented. For example, insome cases, these tubes may be connected using other types of couplingassemblies other than coupling assembly 408 and coupling assembly 410.

With reference now to FIGS. 5-11, illustrations of differentconfigurations for a coupling assembly are depicted in accordance withdifferent illustrative embodiments. The components depicted in FIGS.5-11 may be illustrative examples of how components shown in block formin FIG. 3 may be implemented as physical structures. The differentcomponents shown in FIGS. 5-11 may be combined with components in FIG.3, used with components in FIG. 3, or a combination of the two.

Turning now to FIG. 5, an illustration of components for a couplingassembly is depicted in accordance with an illustrative embodiment. Inthis illustrative example, components for a coupling assembly, such ascoupling assembly 301 in FIG. 3, are depicted. These components may beassembled to form a coupling assembly configured to couple first tube500 with second tube 502. First tube 500 and second tube 502 areexamples of implementations for first transport member 302 and secondtransport member 304, respectively, in FIG. 3.

As depicted, first tube 500 has first end 504, and second tube 502 hassecond end 506. Further, first tube 500 has first surface 508 and firstchannel 510. Second tube 502 has second surface 512 and second channel514.

First ferrule 516, second ferrule 518, first O-ring 520, second O-ring522, sleeve 524, and clamshell device 526 are components that may beassembled to form coupling assembly 528. First ferrule 516 and secondferrule 518 are examples of implementations for first ferrule 326 andsecond ferrule 328, respectively, in FIG. 3. Further, sleeve 524 andclamshell device 526 are examples of implementations for sleeve 340 andclamshell device 346, respectively, in FIG. 3.

First ferrule 516, second ferrule 518, sleeve 524, and clamshell device526 may be comprised of nonmetallic materials having a level ofconductivity within a selected range. This range may be, for example,without limitation, between about 1×10⁻⁴ Siemens/centimeters and about1×10⁻⁹ Siemens/centimeters. For example, first ferrule 516, secondferrule 518, sleeve 524, and clamshell device 526 may be comprised ofcomposite materials. In particular, these components may be comprised ofcomposite materials selected such that these components have a level ofconductivity within the selected range.

First O-ring 520 and second O-ring 522 are examples of implementationsfor first O-ring 342 and second O-ring 344, respectively, in FIG. 3. Inthis illustrative example, each of first O-ring 520 and second O-ring522 is comprised of a viscoelastic material, such as viscoelasticmaterial 332 in FIG. 3. This viscoelastic material has a level ofconductivity within, for example, without limitation, selected range 334for conductivity 335 in FIG. 3.

As depicted, coupling assembly 528 has been partially assembled. Inparticular, first ferrule 516 has been placed around first surface 508of first tube 500 at first end 504 of first tube 500. Second ferrule 518has been placed around second surface 512 of second tube 502 at secondend 506 of second tube 502. Further, first O-ring 520 has been placedaround first ferrule 516, and second O-ring 522 has been placed aroundsecond ferrule 518. In this illustrative example, first O-ring 520 fitsinto a groove in first ferrule 516. Second O-ring 522 fits into a groovein second ferrule 518.

Turning now to FIG. 6, an illustration of a partially-assembled couplingassembly is depicted in accordance with an illustrative embodiment. InFIG. 6, sleeve 524 has been placed around first O-ring 520 and secondO-ring 522 (not shown in this view) of coupling assembly 528 from FIG.5.

When sleeve 524 is placed around these two O-rings, these O-rings arecompressed by sleeve 524. Sleeve 524, first O-ring 520, and secondO-ring 522 form seal 600 when first O-ring 520 and second O-ring 522 arecompressed by sleeve 524. Seal 600 is an example of one implementationfor seal 322 in FIG. 3.

Seal 600 seals the interface (not shown) between first end 504 (notshown) of first tube 500 and second end 506 (not shown) of second tube502. Further, seal 600 forms a conductive pathway between first tube 500and second tube 502. As depicted, coupling assembly 528 remainspartially assembled without clamshell device 526.

Turning now to FIG. 7, an illustration of a fully-assembled couplingassembly is depicted in accordance with an illustrative embodiment. InFIG. 7, coupling assembly 528 has been fully assembled. In particular,clamshell device 526 has been placed around seal 600 and at least aportion of first ferrule 516 and at least a portion of second ferrule518 to form the fully-assembled coupling assembly 528.

With reference now to FIG. 8, an illustration of a cross-sectional viewof a coupling assembly is depicted in accordance with an illustrativeembodiment. In this illustrative example, a cross-sectional view ofcoupling assembly 528 in FIG. 7 taken along lines 8-8 is depicted.

As depicted, seal 600 forms conductive pathway 800 between first tube500 and second tube 502. In particular, conductive pathway 800 is formedat interface 802 between first tube 500 and second tube 502. Interface802 is between first end 504 of first tube 500 and second end 506 ofsecond tube 502. First O-ring 520 fits within groove 806 of firstferrule 516. Second O-ring 522 fits within groove 808 of second ferrule518.

In this illustrative example, conductive pathway 800 is formed throughfirst surface 508 of first tube 500, first ferrule 516, first O-ring520, sleeve 524, second O-ring 522, second ferrule 518, and secondsurface 512 of second tube 502. Conductive pathway 800 allows first tube500, second tube 502, and coupling assembly 528 to function as a groundbetween the two tubes. At least one of first tube 500, second tube 502,and coupling assembly 528 may be connected to ground such thatconductive pathway 800 may be considered as grounding these two tubes.

With reference now to FIG. 9, an illustration of a cross-sectional viewof a different configuration for a coupling assembly is depicted inaccordance with an illustrative embodiment. In FIG. 9, coupling assembly528 has a different configuration than the configuration for couplingassembly 528 in FIG. 8.

As depicted in FIG. 9, coupling assembly 528 includes third O-ring 900and fourth O-ring 902 in addition to first O-ring 520 and second O-ring522 in seal 600. Third O-ring 900 fits within groove 906 of firstferrule 516. Fourth O-ring 902 fits within groove 908 of second ferrule518. Third O-ring 900 and fourth O-ring 902 could also be elastic orviscoelastic features that are not seals, but could be attached toclamshell device 526 to provide a conductive pathway as described below.

In this illustrative example, third O-ring 900 and fourth O-ring 902allow seal 600 to form additional conductive pathway 904 between firsttube 500 and second tube 502. In particular, additional conductivepathway 904 is formed through first surface 508 of first tube 500, firstferrule 516, third O-ring 900, clamshell device 526, fourth O-ring 902,second ferrule 518, and second surface 512 of second tube 502.

Turning now to FIG. 10, an illustration of a cross-sectional view ofanother configuration for a coupling assembly is depicted in accordancewith an illustrative embodiment. In this illustrative example, seal 600in coupling assembly 528 comprises only one O-ring instead of twoO-rings. As depicted, seal 600 uses O-ring 1000 instead of both firstO-ring 520 and second O-ring 522 in FIG. 8.

With this configuration for seal 600, conductive pathway 1002 is formedbetween first tube 500 and second tube 502. Conductive pathway 1002 isformed through first surface 508 of first tube 500, first ferrule 516,O-ring 1000, second ferrule 518, and second surface 512 of second tube502. As depicted, electrical currents may also flow from first ferrule516 into sleeve 524, and into second ferrule 518.

Turning now to FIG. 11, an illustration of a cross-sectional view of adifferent configuration for a coupling assembly is depicted inaccordance with an illustrative embodiment. In this illustrativeexample, seal 600 in coupling assembly 528 comprises gasket 1100.Further, seal 600 does not include sleeve 524 in this example.

As depicted, gasket 1100 has shape 1102. Shape 1102 is configured suchthat first end 1104 of gasket 1100 fits into groove 806 in first ferrule516. Further, shape 1102 is configured such that second end 1106 ofgasket 1100 fits into groove 808 in second ferrule 518. Clamshell device526 may be used to compress gasket 1100 such that gasket 1100 forms seal600 to seal interface 802 when clamshell device 526 is placed aroundseal 600.

In this illustrative example, gasket 1100 forms conductive pathway 1108between first tube 500 and second tube 502. Conductive pathway 1108 isformed through first surface 508 of first tube 500, first ferrule 516,gasket 1100, second ferrule 518, and second surface 512 of second tube502.

The illustrations of the different configurations for coupling assembly528 in FIGS. 5-11 are not meant to imply physical or architecturallimitations to the manner in which an illustrative embodiment may beimplemented. Other components in addition to or in place of the onesillustrated may be used. Some components may be optional.

With reference now to FIG. 12, an illustration of a process for reducingan intensity of an electrical discharge within a fluid transport systemin the form of a flowchart is depicted in accordance with anillustrative embodiment. The process illustrated in FIG. 12 may beimplemented using fluid transport system 100 in FIG. 1. In thisillustrative example, fluid transport system 100 may be configured foruse in aerospace vehicle 106 in FIG. 1.

The process begins by operating the aerospace vehicle in which the fluidtransport system has an electrical configuration comprising a set ofelectrical properties in which each electrical property in the set ofelectrical properties has a value within a selected range (operation1200). The process may then reduce an intensity of an electricaldischarge within the fluid transport system during operation of theaerospace vehicle to within selected tolerances by the electricalconfiguration of the fluid transport system (operation 1202), with theprocess terminating thereafter.

With reference now to FIG. 13, an illustration of a process for reducingthe energy that can be supplied to an electrical discharge within afluid transport system in the form of a flowchart is depicted inaccordance with an illustrative embodiment. The process illustrated inFIG. 13 may be implemented using fluid transport system 100 in FIG. 1.In particular, this process may be implemented using tube 201 in FIG. 2.Tube 201 may be configured for use in aerospace vehicle 106 in FIG. 1.

The process begins by operating the aerospace vehicle in which atransport member in the fluid transport system in the aerospace vehicleis comprised of a material selected such that the transport member has aresistance within a selected range (operation 1300). This selected rangemay include only electrical resistance levels above about 100 kilohms.Further, in some cases, this selected range may also only includeelectrical resistance levels below about 100 megohms.

The process may then reduce voltages and currents, induced in responseto an electromagnetic event that occurs during operation of theaerospace vehicle, along the transport member to within selectedtolerances by the resistance of the transport member (operation 1302),with the process terminating thereafter. Reducing these voltages andcurrents may reduce the energy that can be supplied to an electricaldischarge within the fluid transport system. In this manner, thisreduction of the induced voltages and currents may reduce the intensityof an electrical discharge that may occur within the fluid transportsystem.

With reference now to FIG. 14, an illustration of a process fordissipating electrostatic charge in the form of a flowchart is depictedin accordance with an illustrative embodiment. The process illustratedin FIG. 14 may be implemented using a coupling assembly, such as, forexample, coupling assembly 301 in FIG. 3.

The process begins by operating the aerospace vehicle such that anelectrostatic charge builds up on a surface of at least one of a firsttransport member and a second transport member in the fluid transportsystem in the aerospace vehicle (operation 1400). In one illustrativeexample, a first end of the first transport member may be coupled to asecond end of the second transport member using a connection in the formof a coupling assembly comprising a first fitting, a second fitting, anda seal. The first fitting may be associated with the first end of thefirst transport member. The second fitting may be associated with thesecond end of the second transport member.

The seal is placed around the first fitting and the second fitting withthe first end of the first transport member positioned next to thesecond end of the second transport member. The seal is configured toseal an interface between the first end of the first transport memberand the second end of the second transport member when the first end andthe second end are positioned next to each other.

In one illustrative example, the seal includes a first gasket, a secondgasket, and a sleeve. The first gasket is placed around the firstfitting, and the second gasket is placed around the second fitting. Thesleeve is then placed around the first gasket and the second gasket. Thesleeve compresses the first gasket and the second gasket to seal theinterface between the first end of the first transport member and thesecond end of the second transport member. The coupling assembly betweenthe first transport member and the second transport member may beconfigured to form a conductive pathway between the first transportmember and the second transport member.

The process dissipates the electrostatic charge that builds up on thesurface of the at least one of the first transport member and the secondtransport member during operation of the aerospace vehicle, using theconductive pathway between the first transport member and the secondtransport member (operation 1402), with the process terminatingthereafter. In this manner, the coupling assembly allows the firsttransport member and the second transport member to be grounded from onetransport member to the other. A number of electrical currents may flowfrom one transport member to the other transport member withoutinterruption and without the level of the electrical currents changingoutside of selected tolerances.

The flowchart and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of apparatuses and methods in an illustrativeembodiment. In this regard, each block in the flowcharts or blockdiagrams may represent a module, segment, function, and/or a portion ofan operation or step.

In some alternative implementations of an illustrative embodiment, thefunction or functions noted in the blocks may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be performed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added in addition tothe illustrated blocks in a flowchart or block diagram.

Illustrative embodiments of the disclosure may be described in thecontext of aircraft manufacturing and service method 1500 as shown inFIG. 15 and aircraft 1600 as shown in FIG. 16. Turning first to FIG. 15,an illustration of an aircraft manufacturing and service method isdepicted in accordance with an illustrative embodiment. Duringpre-production, aircraft manufacturing and service method 1500 mayinclude specification and design 1502 of aircraft 1600 in FIG. 16 andmaterial procurement 1504.

During production, component and subassembly manufacturing 1506 andsystem integration 1508 of aircraft 1600 takes place. Thereafter,aircraft 1600 may go through certification and delivery 1510 in order tobe placed in service 1512. While in service 1512 by a customer, aircraft1600 is scheduled for routine maintenance and service 1514, which mayinclude modification, reconfiguration, refurbishment, and othermaintenance or service.

Each of the processes of aircraft manufacturing and service method 1500may be performed or carried out by a system integrator, a third party,and/or an operator. In these examples, the operator may be a customer.For the purposes of this description, a system integrator may include,without limitation, any number of aircraft manufacturers andmajor-system subcontractors; a third party may include, withoutlimitation, any number of vendors, subcontractors, and suppliers; and anoperator may be an airline, a leasing company, a military entity, aservice organization, and so on.

With reference now to FIG. 16, an illustration of an aircraft isdepicted in which an illustrative embodiment may be implemented. In thisexample, aircraft 1600 is produced by aircraft manufacturing and servicemethod 1500 in FIG. 15 and may include airframe 1602 with systems 1604and interior 1606. Examples of systems 1604 include one or more ofpropulsion system 1608, electrical system 1610, hydraulic system 1612,environmental system 1614, and fuel system 1616. Fuel system 1616 andhydraulic system 1612 may be implemented using, for example, fluidtransport system 100 in FIG. 1.

Any number of other systems may be included in systems 1604, dependingon the implementation. Although an aerospace example is shown, differentillustrative embodiments may be applied to other industries, such as theautomotive industry.

Apparatuses and methods embodied herein may be employed during at leastone of the stages of aircraft manufacturing and service method 1500 inFIG. 15. For example, tubes, such as plurality of tubes 111 in FIG. 1,may be manufactured, installed, and/or reworked in aircraft 1600 duringat least one of component and subassembly manufacturing 1506, systemintegration 1508, and maintenance and service 1514.

In one illustrative example, components or subassemblies produced incomponent and subassembly manufacturing 1506 in FIG. 15 may befabricated or manufactured in a manner similar to components orsubassemblies produced while aircraft 1600 is in service 1512 in FIG.15. As yet another example, one or more apparatus embodiments, methodembodiments, or a combination thereof may be utilized during productionstages, such as component and subassembly manufacturing 1506 and systemintegration 1508 in FIG. 15. One or more apparatus embodiments, methodembodiments, or a combination thereof may be utilized while aircraft1600 is in service 1512 and/or during maintenance and service 1514 inFIG. 15. The use of a number of the different illustrative embodimentsmay substantially expedite the assembly of and/or reduce the cost ofaircraft 1600.

Thus, the different illustrative embodiments provide a method andapparatus for reducing an intensity of an electrical discharge that mayoccur within a fluid transport system. In one illustrative embodiment, afluid transport system comprises a plurality of transport members and anumber of connections connecting transport members in the plurality oftransport members to each other. The plurality of transport members andthe number of connections may be comprised of materials selected suchthat the intensity of an electrical discharge that occurs within thefluid transport system may be reduced to within selected tolerances.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different features as compared to otherdesirable embodiments. The embodiment or embodiments selected are chosenand described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

1. A coupling assembly comprising: a first fitting associated with afirst end of a first transport member; a second fitting associated witha second end of a second transport member; and a seal configured forplacement around the first fitting and the second fitting when the firstend of the first transport member is positioned relative to the secondend of the second transport member, wherein the seal is furtherconfigured to seal an interface between the first end of the firsttransport member and the second end of the second transport member, andwherein the seal is comprised of a material configured such that theseal has a level of conductivity within a selected range and such that aconductive pathway is formed between the first transport member and thesecond transport member.
 2. The coupling assembly of claim 1, whereinthe selected range is between about 1×10⁻⁴ Siemens/centimeters and about1×10⁻⁹ Siemens/centimeters.
 3. The coupling assembly of claim 1, whereinthe material is a viscoelastic material and wherein the seal comprises:a first gasket configured to be received by the first fitting, whereinthe first gasket comprises the viscoelastic material having the level ofconductivity within the selected range; and a second gasket configuredto be received by the first fitting, wherein the second gasket comprisesthe viscoelastic material having the level of conductivity within theselected range.
 4. The coupling assembly of claim 3, wherein the sealfurther comprises: a sleeve configured for placement around the firstgasket and the second gasket when the first end of the first transportmember is positioned relative to the second end of the second transportmember, wherein the sleeve compresses the first gasket and the secondgasket to seal the interface between the first end of the firsttransport member and the second end of the second transport member. 5.The coupling assembly of claim 4, wherein the conductive pathway isformed such that an electrical current is allowed to flow in at leastone of a first direction from the first transport member, through thefirst fitting, through the first gasket, through the sleeve, through thesecond gasket, and through the second fitting to the second transportmember and in a second direction from the second transport member,through the second fitting, through the second gasket, through thesleeve, through the first gasket, and through the first fitting to thefirst transport member.
 6. The coupling assembly of claim 4, wherein thefirst fitting, the second fitting, the first gasket, the second gasket,and the sleeve are comprised of nonmetallic materials having the levelof conductivity within the selected range.
 7. The coupling assembly ofclaim 3, wherein the first gasket is a first O-ring and the secondgasket is a second O-ring.
 8. The coupling assembly of claim 1, whereinan electrical current induced in at least one of the first transportmember and the second transport member by electrostatic charge thatbuilds up on the at least one of the first transport member and thesecond transport member is conducted along the conductive pathway. 9.The coupling assembly of claim 1, wherein the seal comprises: a gasketcomprising a viscoelastic material having the level of conductivitywithin the selected range, wherein the conductive pathway is formedbetween the first transport member and the second transport memberthrough the gasket, and wherein compression of the gasket seals theinterface between the first transport member and the second transportmember.
 10. The coupling assembly of claim 1 further comprising: a coverconfigured to cover the seal and hold the seal in place.
 11. Thecoupling assembly of claim 10, wherein the cover is a clamshell device.12. The coupling assembly of claim 10, wherein the cover comprises anonmetallic material having the level of conductivity within theselected range and is configured to form a portion of the conductivepathway between the first transport member and the second transportmember.
 13. The coupling assembly of claim 1, wherein the material is aviscoelastic material that comprises a conductive elastomer having thelevel of conductivity within the selected range.
 14. The couplingassembly of claim 1, wherein the seal is configured to seal theinterface between the first end of the first transport member and thesecond end of the second transport member by reducing a possibility ofmaterial flowing at least one of into and out of a channel formed by thefirst transport member and the second transport member when the firsttransport member and the second transport member are coupled to eachother using the coupling assembly.
 15. The coupling assembly of claim 1,wherein the first transport member and the second transport member arefuel transport members in a fuel system for an aerospace vehicle inwhich the fuel system has an overall level of conductivity within theselected range.
 16. A fuel system comprising: a first transport member;a second transport member; and a coupling assembly configured to couplea first end of the first transport member to a second end of the secondtransport member, wherein the coupling assembly comprises: a firstfitting associated with the first end of the first transport member andhaving a level of conductivity within a selected range; a second fittingassociated with the second end of the second transport member and havingthe level of conductivity within the selected range; a first gasketconfigured for placement around the first fitting, wherein the firstgasket comprises a viscoelastic material having the level ofconductivity within the selected range; a second gasket configured forplacement around the second fitting, wherein the second gasket comprisesthe viscoelastic material having the level of conductivity within theselected range; and a sleeve configured for placement around the firstgasket and the second gasket and having the level of conductivity withinthe selected range in which the sleeve is configured to compress thefirst gasket and the second gasket to form a seal that seals aninterface between the first end of the first transport member and thesecond end of the second transport member when the first end of thefirst transport member is positioned relative to the second end of thesecond transport member, wherein the seal forms a conductive pathwaybetween the first transport member and the second transport memberthrough the first fitting, the seal, and the second fitting.
 17. Thefuel system of claim 16, wherein the first gasket is a first O-ring, thesecond gasket is a second O-ring, and the viscoelastic material is aconductive elastomer.
 18. The fuel system of claim 17, wherein thecoupling assembly further comprises: a cover configured to cover thefirst gasket, the second gasket, the sleeve, at least a portion of thefirst fitting, and at least a portion of the second fitting.
 19. Amethod for conducting an electrical current between a first transportmember and a second transport member in a fuel system in an aerospacevehicle, the method comprising: operating the aerospace vehicle suchthat an electrical charge builds up around a surface of at least one ofthe first transport member and the second transport member in the fuelsystem in the aerospace vehicle, wherein a first end of the firsttransport member is coupled to a second end of the second transportmember using a first fitting associated with the first end of the firsttransport member, a second fitting associated with the second end of thesecond transport member, and a seal, wherein the seal is configured toseal an interface between the first end of the first transport memberand the second end of the second transport member when the first end ofthe first transport member is positioned relative to the second end ofthe second transport member, and wherein the seal is comprised of amaterial configured such that the seal has a level of conductivitywithin a selected range and such that a conductive pathway is formedbetween the first transport member and the second transport member; anddissipating electrostatic charge that builds up on at least one of thefirst transport member and the second transport member during operationof the aerospace vehicle using the conductive pathway formed by the sealbetween the first transport member and the second transport member. 20.The method of claim 19, wherein dissipating the electrostatic chargecomprises: dissipating the electrostatic charge that builds up on atleast one of the first transport member and the second transport memberusing the conductive pathway formed by the seal, wherein the selectedrange for the level of conductivity for the seal is between about 1×10⁻⁴Siemens/centimeters and about 1×10⁻⁹ Siemens/centimeters.